The present invention relates to a draw-in device for drawing an endless belt, like a wire or a felt, into a paper making machine, cardboard making machine, or the like. Such a draw-in device is known from Federal Republic of Germany Pat. No. 2,439,261.
Wires or felts of paper making machines are each in the form of an endless belt which forms a belt loop. The felts or wires used are frequently rather stiff and therefore can be neither folded nor gathered. In the case of wires, gathering is not permissible since the wire would be damaged.
Such belt loops travel over rotatable cylinders, press rolls, guide rolls, or the like, along an endless path. The rolls are mounted for rotation in frame parts located on the guide side of the machine and on the opposite drive side of the machine. The rolls, which are typically part of the frame, are arranged within the belt loop. Frequently, two belt loops are arranged one above the other. This further complicates the drawing in of the belt loops. The difficulty in the drawing in occurs because the supports for the rolls, which are typically part of the frame, do not permit the axial drawing in of the belt loop over these inner rolls. In order to nevertheless apply the endless belt loop onto the inner rolls without interference, three fundamental systems have been employed in the past.
(a) The removal system:
All rolls and supports which are arranged within the belt loop, as well as any other parts which extend through the belt loop, are removed individually or jointly from the machine. After the belt loop is placed into the machine, those rolls, supports and parts are passed through the belt loop and are again fastened to the frames or foundation.
(b) The cantilever foundation:
All rolls and other parts which extend through the belt loop are clamped firmly to one of the two side frames or foundation sides. Upon removal of intermediate pieces from the side frame on the other side, these rolls and parts freely protrude to that other side and are cantilevered, which permits the belt loop to be introduced around these protruding parts from that other side. The intermediate pieces are thereafter reinserted.
(c) The push-on system:
Lengthening or extension supports are fastened to the protruding journals of the rolls or to corresponding fastening points of the frame which holds the one end of the rolls and also holds the other parts present within the belt loop. The belt loop is placed over these extension supports. As a second step, these extension supports are lifted up outside the belt loop. Intermediate pieces on the frames are removed, and the belt loop is introduced laterally into the operating position. The intermediate pieces are reinserted and the extension supports are, as a rule, then removed.
In the case of belt loops which are arranged one above the other, combinations of these systems are of course also possible in which, for instance, the lower belt loop is installed under tension in accordance with system (a) and the upper belt loop is installed in accordance with system (c).
It is also known upon the installation of a belt loop onto a frame to use a removable, short auxiliary support, shaped similarly to a C-shaped piece with the arms extending toward the main frame The belt loop is placed over the upper arm and the vertical stem of the C-shaped piece. The end of the auxiliary support is used to hold the frame part which holds the inner rolls, etc. which pass through the belt loop, during the removal of the intermediate pieces (Federal Republic of Germany Pat. No. 2,439,261). While this method does make a light weight auxiliary support possible, it has the disadvantage that the belt loop must be bent and be moved against gravity upon the drawing in. It would be conceivable to extend the upper arm of the known auxiliary support to such an extent that there is space for the entire width of the belt on it. In that case, however, the arm would have a very great unsupported length. Furthermore, since large masses, which the auxiliary support must temporarily support, rest on the frames of the paper making machine, such an auxiliary support would be very bulky, heavy and difficult to handle. A crane of particularly high capacity would have to be installed in order to move such an auxiliary support. The floor, which is the ceiling of the cellar alongside the machine, would have to be made particularly strong in order to prevent the auxiliary support from breaking through the floor solely by its own weight. For these reasons, this system has not been used, and was not even been considered, for two-belt loops arranged one over the other.